A118490 Squares for which both the sum of the digits and the product of the digits is a triangular number.

0, 1, 100, 3025, 5041, 6400, 10000, 21025, 23104, 26569, 32041, 36100, 38809, 47089, 63001, 87616, 88804, 110224, 122500, 130321, 157609, 170569, 178084, 195364, 199809, 201601, 203401, 209764, 211600, 218089, 300304, 302500, 351649, 395641

Offset

1,3

Links

Table of n, a(n) for n=1..34.

Example

26569 is in the sequence because (1) it is a square, (2) the sum of its digits is 2+6+5+6+9=28, (3) the product of its digits is 2*6*8*6*9=3240, (4) 28 and 3240 are both triangular numbers.

Mathematica

trnos=Accumulate[Range[0, 1000]];
spdQ[n_]:=Module[{idn=IntegerDigits[n]}, MemberQ[trnos, Total[idn]]&&MemberQ[trnos, Times@@idn]]; Select[Range[0, 650]^2, spdQ] (* Harvey P. Dale, Mar 05 2011 *)

Crossrefs

Cf. A000217.

Sequence in context: A250845 A200937 A112889 * A146310 A117685 A091134

Adjacent sequences: A118487 A118488 A118489 * A118491 A118492 A118493

Keyword

base,nonn

Author

Luc Stevens (lms022(AT)yahoo.com), May 05 2006

Status

approved